A conventional apparatus operating a hydraulic actuator for opening and closing a valve has employed a hydraulic power pack.
However, in the valve opening/closing system which uses the hydraulic power pack for operating the hydraulic actuator for opening and closing the valve, when power is cut off by a stoppage of power supply and the like, the hydraulic actuator for opening and closing the valve can not be operated. Further, there is a disadvantage that a separate power supplying device should be provided to operate the hydraulic actuator.